1. Field of the Invention
The present invention is related to an engine air particle separator and filter assembly.
2. Description of Related Art
Rotary-wing aircraft often operate utilizing various types of combustion engines. Inherent in the operation of these engines is that air continuously flows through an intake on the outer periphery of the rotary-wing aircraft and into the engine. The air will then mix with the fuel resulting in a mixture of fuel to air that has optimum ratios. The fuel/air mixture is then subjected to a spark and the mixture is ignited. The resulting explosion provides the force that is necessary to drive the various engine components.
Rotary-wing aircraft operate in a variety of environmental conditions. The various conditions result in air that contains impurities of various sizes and composition. For example, the air in an urban environment may contain impurities of relatively larger sizes, such as leaves, while the air in a desert may contain impurities of relatively smaller sizes, such as grains of sand. In addition, rotary-wing aircraft operate in a variety of temperatures depending on the time of year and geographical location. In very cold temperatures, freezing of the engine components may occur unless preventative action is taken.
Currently, engine air particle separators (EAPS) and barrier filter systems are used to filter the air prior to entering the rotary-wing aircraft's engine. The environmental conditions in which the rotary-wing aircraft often determines whether EAPS or barrier filters will be used. For example, EAPS may be more suitable to use when the air contains impurities of relatively larger sizes or in freezing temperatures. On the other hand, barrier filter technology may prove to be more suitable in desert-like environments where the air contains impurities of relatively smaller sizes, e.g., grains of sand.
As shown in FIG. 2, currently available EAPS include a plurality of individual centrifugal separator swirl tubes which are located in two panels. In use, engine air particle separators (EAPS) are sized and configured to be mounted ahead of the engine inlet ducts and are designed to reduce the erosion of the aircraft engines due to sand and dust ingestion. Moreover, EAPS are configured to discharge dirty air overboard through a scavenge system powered by an electric blower while allowing cleaned air to enter the engine inlet.
Additionally, EAPS require virtually no cleaning since there is not a buildup of filtered impurities in the unit. Thus, the engine power penalty remains substantially constant with time. In addition, EAPS have been shown to operate successfully in some icing conditions. Thus, not only do the EAPS operate as a particle separator, but it also provides a level of ice protection for the engine as well. The level of ice protection depends upon the orientation of the swirl tubes to the free stream airflow. Prior to the development of EAPS, the inlet ducts, as shown in FIG. 3, were equipped with integral electric heating elements to prevent the formation of ice on the engine. In using EAPS, the integral electric heating elements can either be disabled or removed.
Field experience has shown that EAPS may provide inadequate particle separation efficiency in severe sand and dust operational environments. This is mainly due to the relatively low efficiency of the swirl tubes to remove very fine particles from the inlet air stream. As a result, an unacceptable level of engine erosion protection may result.
In environments such as these, vehicles are often equipped with barrier filters. Barrier filter technology, in contrast with EAPS technology, has been shown to provide satisfactory engine erosion protection in sandy and dusty environments. Barrier filters are capable of separating approximately 99% of very fine particles. The particles that are filtered from the air are retained in the filter. As the sand and dust accumulates in the filter, power of the engine is compromised resulting in decreased performance of the aircraft. Consequently, the filters require servicing at regular intervals in order to remove the dirt and dust.
Currently there is no quick and inexpensive way to switch from the use of an EAPS with vortex tube technology and to an assembly using barrier filter panels. Currently, such a change requires the filter system as a whole must be removed from the rotary-wing aircraft and replaced with another filter system. The capability to quickly and inexpensively change between vortex tubes and barrier filter panels would be beneficial to the owner of the aircraft.